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<html lang="zh">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <script src="jquery-1.12.4.js"></script>
    <title>Document</title>
</head>

<body>
    <ul>
        <li>1</li>
        <li id="byid">2</li>
        <li class="green">3</li>
    </ul>
    <div id="byid">22</div>
    <div class="green">33</div>
</body>
<script>
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        $('li').css('background', 'pink')
        $('div').css('color', 'red')

        $('#byid').css('fontSize','20px')
        $('.green').css('color','green')

        $("*").css('fontSize','40px')

        $('div,.green').css('color','red')
        $('li.green').css('color','cyan')
    })
</script>

</html>